Electric commutator



' Nov. 14, 1939. E. H. STIVENDER ELECTRIC COMMUTATOR Filed May 4, 1936Patented Nov. 14, 1939 UNITED STATES PATENT OFFlCE ELECTRIC COMMUTATORApplication May 4, 1936, Serial No. 77,669

3 Claims.

This invention relates in general to improvements in commutators, andmore particularly to a commutator structure consisting of segmentsfastened independently of each other on a com- 5 mon insulating supportand which may be utilized in dynamo electric machines, in rheostats, andin any other control apparatus requiring a commutator presenting acylindrical contact path.

Commutators presenting a cylindrical contact path are generallyconstituted of Wedge shaped segments, which may be insulated from eachother and from their support by means of mica and are clamped togetheror which may be imbedded in a mass of molded insulation. Both suchconstructions present the disadvantages of being expensive and ofprecluding the removal and replacement of any segment which may bedefective or of tightening up loose segments. It is more economical toutilize segments constituted by extensions of a plurality of studs arranged in one row or in a plurality of rows and severally fastened on acommon supporting plate of insulating material, the extensions beinginterleaved to form a single cylindrical contact path; If the brushcooperating with the commutator is in the form of a rocking sector, thecommutator is not subject to wear and may be plated with a metal givinga low contact resistance with the sector. Means must then be providedfor guiding the sector to prevent it from moving out of engagement withthe commutator.

It is, therefore, one of the objects of the present'invention to providea commutator present- 35 ing a cylindrical contact path formed ofsegments independently fastened on a common insulating support.

Another object of the present invention is to provide a commutatorpresenting a cylindrical contact path formed of segments constituted byextensions of studs mounted on a common insulating plate.

Another object of the present invention is to provide a commutatorpresenting a cylindrical contact path formed of segments constituted orinterleaved extensions of studs arranged in a plurality of rows.

Objects and advantages other than those above set forth will be apparentfrom the following description when read in connection with theaccompanying drawing, in which:

Fig. l is a view in elevation of one embodiment of the present inventionconsisting of a commutator comprising segments formed of the extensionsof two rows of studs arranged on adjacent concentric arcs of circle andcooperating with a brush of the rocking sector type; and

Fig. 2 is a cross-section taken in the plane of the line IIII in Fig. 1.

Referring'more particularly to the drawing by characters of reference,reference numeral 6 designates a panel which is preferably made ofmetal, and is designed to support a commutator or a plurality ofcooperating commutators with the cooperating brushes thereof and thebrush actuating means. The drawing shows only a portion of panel Bsupporting a single commutator comp-rising a plate I of insulatingmaterial of suitable shape fastened on panel 6 by means of bolts 8 andcovering an aperture through the panel 6, which aperture is shaped as asector of an annulus. Plate l is accurately located with respect topanel 6 by means of dowel pins 9 penetrating therethrough and is made ofa suitable insulating material, such as laminated Bakelite orimpregnated asbestos, and is provided with a plurality of holes toreceive a plurality of conductive studs l0 preferably made of brass, ofwhich only four are shown in Figure 2 to retain simplicity in thedrawing. The studs penetrate through the plate I and are fastenedtherein by means of nuts II, and are preferably arranged in two adjacentconcentric circular rows. The studs carry brackets I 2 to support thedifferent sections of a resistor it in conductive contact with the studsto thereby permit a variable number of sections of the resistors to beconnected in a circuit by means of the commutator. Only two sections ofresistors I3 are shown in Figure 2, but it will be understood that ingeneral each segment of one row is connected with the two adjacentsegments of the other row through two sections of the resistor. Thestuds are knurled on a portion of the length thereof, the projections ofthe knurled portions engaging with the walls of the complementary holesof plate 7 to thereby prevent the studs from turning when the nutsthereof are tightened.

The studs are provided with extensions shaped differently dependent onthe number of rows of studs employed. In the embodiment hereinillustrated, two rows of studs being used, the studs of the inner roware each provided with an extension l4 coaxial therewith and preferablyobtained by milling from material integral with the stud. The studs ofthe outer row are each provided with an L-shaped extension, the portionof the extension coaxial with the stud being formed ofmaterial integralwith the stud having a slot reoeiving a rectangular strip of brasssoldered therein. The extensions of all the studs penetrate through theaperture of panel 6 and extend beyond the surface of the panel, and arearranged in side by side spaced relation, the extensions [4 and [6 beinginterleaved to form the segments of the commutator which are machinedafter assembly of the studs to form a single cylindrical contact path.It will be seen that although a single row of studs could be used, therewould be insufiicient space for the nuts thereof unless such nuts wereof a diameter less than the distance between the axes of adjacentsegments, thus generally limiting the diameter of the studs to a too lowvalue. When two rows of studs are utilized, the diameter of the nuts maybe increased to substantially the distance between the axes of alternatesegments, and a strong and rigid construction may then be obtained bycorrespondingly increasing the diameter of the studs. If it is desiredto further increase the rigidity of the commutator, the diameter of thestuds may be further increased, such studs then being arranged in threeor more rows instead of in only two rows, the extensions thereof beingsuitably shaped and interleaved to form a single cylindrical contactpath.

The assembly of the commutators comprises the steps of drilling aplurality of rows of holes on the circumferences of concentric circlesin plate I, forcing studs I!) in such holes, fastening the studs bymeans of nuts I l, grinding the contact path and plating extensions l4and It by immersing such extensions exclusively of plate 1 in a platingbath. The contact path is machined by grinding in preference to turningwith a lathe tool for the reason that the segments are laterallyunsupported and could not be machined with a coarse tool and anaccurately polished surface is thus more rapidly obtained by grinding.The segments should then be made of a metal which takes a high polish bygrinding, brass being accordingly preferred to copper. The surface ofthe contact path must then be plated either with a metal which does nottarnish when subjected to the ambient atmosphere such as chromium, orwith a metal which retains a low contact resistance even when tarnished,such as silver. In general it is not desirable to immerse plate I in theplating bath, and only extensions ]4 and "5 are immersed in the bath andplated. Because the extensions are insulated from each other and frompanel 6 only by air, the extensions may be plated on all sides to withina short distance of plate 1. If desired, the entire studs and theirextensions may also be plated prior to being assembled in plate "I toinsure that the surfaces of extensions I l, l6 other than the surfacesthereof forming the contact path may be cleaned properly beforereceiving any of the plating metal.

The commutator above described is more particularly adapted to engagewith the rim ll of a conductive section l8 presenting a cylindricalcontact surface arranged to engage with the contact path of thecommutator. Rim I1 is preferably made of graphite, and sector I8 ispreferably made of light sheet metal provided with a needle point l9resting in a jeweled cup 2! mounted on a spindle 22 through a spring 23.The spindle may be caused to oscillate by means of a link 24 connectedwith any suitable actuating means (not shown), the spindle thenimparting to sector [8 a rocking movement on the contact path of thecommutator. Spring 23 urges sector I8 in contact with the commutator,and a pair of springs 26 acting between sector I8 and panel 1 throughinsulated extensions of bolts 8 prevent sliding movement of sector l8 onthe contact path under the action of gravity in directions in a planeparallel to the panel. A pair of guides 21 mounted on panel I preventmovement of sector IS in a direction perpendicular to the panel. SectorI8 is connected by means of a flexible conductor 28 with an insulatedterminal 29 mounted on panel 1. The circuit in which resistor I3 is tobe variably inserted, such as the field circuit of a dynamo-electricmachine for example, is then connected with terminal 29 and with asuitable one of studs l0.

Although but one embodiment of the present invention has beenillustrated and described, it will be apparent to those skilled in theart that various changes and modifications may be made therein withoutdeparting from the spirit of the invention or from the scope of theappended claims.

I claim:

1. In control apparatus, a metallic panel having an aperture, a plate ofinsulating material fastened on said panel and covering said aperture, aresistor having a plurality of sections, a plurality of conductive studsextending through said plate and fastened therein, said studs beingarran ed in a plurality of adjacent concentric circular rows and havinginterleaved extensions penetrating through said aperture and insulatedby air from each other and from said panel to form the segments of acommutator, said commutator presenting a cylindrical contact path andhaving means for supporting the sections of said resistor on said studsin conductive relation therewith, a conductive sector having acylindrical contact surface arranged to engage said contact path, meansfor imparting to said sector a rocking movement on said contact path,spring means acting between said sector and said panel to preventsliding movement of said sector on said contact path in directions in aplane parallel to said panel, and guide means for preventing movement ofsaid sector in a direction perpendicular to said panel.

2. In control apparatus, a supporting member,

a resistor having a plurality of sections, a plurality of studs ofelectrically conductive mate rial extending through said member inmutual insulating relation, said studs being arranged in a plurality ofadjacent concentric rows and having interleaved extensions insulated byair from each other to form the segments of a commutator, saidcommutator presenting a cylindrical contact path and having means forsupporting the sections of said resistor on said studs in electricallyconductive relation therewith, a conductive sector having a cylindricalcontact surface arranged to engage said contact path, means forimparting to said sector a rocking movement on said contact path, andmeans actingto. prevent sliding movement of said sector in a planeperpendicular to the axis of said contact path and in a directionparallel to the axis of said contact path.

3. In a control apparatus, a plate of insulating material, a pluralityof studs of electrically conductive material passing through said plateand insulated from each other therein and arranged in a plurality ofparallel rows, said studs being severally connected by sections of aresistor, end portions of said studs being provided with reducedextensions supported only by said studs,

the reduced extensions of the studs of one row"75* extending onlyaxially of said studs, and the reduced extensions of the studs of theother row having a portion projecting towards the said one row and beinginterleaved with and in spaced relation to the reduced extensions of thestuds of said one row, and a face of all of the interleaved reducedextensions of said studs being disposed in a single discontinuoussurface serving as a commutator surface, and a movable contact devicecooperative with said commutator surface of the extension of said studsfor Icy-passing sections of said resistor.

EDWARD H. STIVENDER.

